There have been many recent developments in the manage- ment of breast cancer. In general, treatment is becoming more patient- and tumour-specific. This is true for both surgi- cal and systemic treatment. In this article I consider the role of sentinel node biopsy.
Sentinel node biopsy techniques were developed in the 1960s to look for metastatic involvement of lymph nodes in parotid cancer. The principle is based on an assumption of a ‘sentry’ lymph node that guards the nodal basin. If the
‘first’ or sentinel node is not involved, then the remainder of the chain is unlikely to be involved. Since then, it has been finding its place in the management of various cancers. It is now a technique that is used world-wide to look for spread from breast cancer and melanoma. An increasing number
of surgeons are using the technique to look for lymphatic spread from gastrointestinal tumours as an adjuvant to mini- mally invasive surgery. However, it is now established man- agement in early breast cancer.
The management of breast cancer is based on the T, N, M concept of cancer progression. In the case of blood-borne metastatic disease, the primary treatment is systemic. For the primary tumour of the breast, treatment consists of any combination of surgery, systemic treatment and radiothera- py, dependent on the stage of disease. For early breast cancer, the mainstay of treatment is surgery. If nodes are palpable at the time of presentation (i.e. the patient is N1/N2) the patient requires a standard axillary dissection.
The management of the NO axilla presents its own prob- lems and it is this area that is addressed by sentinel node biopsy.
The standard treatment for patients with operable breast cancer is to have an axillary dissection. The reason for this is twofold — accurate staging of the patient and treatment of local disease. This is not without its problems.
Postoperative morbidity is often caused by the axillary dis- section rather than the primary breast procedure. However, the status of the axilla is an important guide for the oncolo- gists in their treatment. If patients are found to have axillary involvement they are more likely to have adjuvant therapy.
Local control in the axilla is rarely a problem so there has been a growing trend to more conservative means of diag- nosing the axillary status.
Methods of assessing the axilla in clinically node-negative patients
Clinical examination.Nodal examination has a high sensitivity but low specificity. The finding of an ‘NO’ status may underestimate the axillary status. The likelihood of a patient having nodal involvement if there is clinical absence of disease is dependent on the tumour size. For example, if patients have a clinical assessment of a T1 NO tumour, they have a 5% chance of having nodal involvement on axillary dissection. If the tumour is T2 NO (> 5 cm), that rises to 47%.
Axillary dissection.A complete axillary dissection has many complications. The commonest is seroma formation, but the patient will permanently have some loss of sensation
Sentinel node biopsy — its
application in the management of early breast cancer
Dr Jenny Edge is a general surgeon with a particular interest in breast cancer. She is in practice at the Christiaan Barnard Memorial Hospital (formerly City Park) in Cape Town. She also holds a part-time position at the Breast Clinic at Groote Schuur Hospital.
After graduating in medicine from the University of London, she moved to work in New Zealand with her husband, where they stayed for 5 years. On returning to South Africa, she entered the surgical rotation at
Tygerberg Hospital, where he became a consultant gener- al surgeon after specialising.
Before studying medicine, Jenny took a BSc in anthropol- ogy, also from the University of London, and she also has a BSc in epidemiology and statistics from the University of Stellenbosch. She is married to Tony Brutus and they have 2 children, Jerome and Matthew.
Jenny Edge
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down the ipsilateral arm. Marked lymphoedema is rare but many patients may feel asymmetry of their arms after a dis- section.
Axillary samplingis a technique that was used in sever- al large centres in the world before sentinel node biopsy.
Random samples of nodes are removed from the axilla. In those centres that advocate its use, good supporting data show that sentinel node biopsy is as accurate as axillary dissection in staging the axilla in the hands of their sur- geons.
Imaging.Radiological techniques have flourished in the last decade. There have been many studies looking at the axilla using ultrasound. These techniques can be useful if the node contains a lot of tumour but are less reliable in identifying small nodes that have lymphatic spread.
Some surgeons advocate leaving the axilla and following up the patient. This is reasonable in an older population but not advisable in young women (< 70 years) with breast cancer.
The problem of what to do with patients with no palpable nodes remains. If they are all subjected to an axillary dis- section, up to 90% of those with small tumours would have unnecessary surgery but conversely, treated conservatively, a proportion of those with axillary involvement would be understaged and therefore undertreated.
Sentinel node biopsy — the technique Although there is variation in different centres, there are 2 main techniques that are commonly employed — a simple blue dye injection at the time of surgery and a lymphoscin- tiogram done preoperatively and the tracing of the radionu- clide intraoperatively. The combination of both techniques gives the best results and that is what will be described here.
Twenty-four hours (or less) before the surgery, the patient has the tumour or surrounding breast area injected with radionuclide. The most commonly used substance is tech- netium-labelled nanocolloid (Tc 99m). A preoperative scan is performed at 15 minutes and again at 2 hours. The scan gives two vital pieces of information — the location of the nodes (axillary/intramammary) and how many nodes are involved. Often, there is one sentinel node and one/two eschelon nodes.
At the time of surgery, the tumour is injected with a blue dye. Intraoperatively, an incision is made in the axillary area and the sentinel node is sought using a hand-held gamma camera and, visually, looking for the blue leading to the node. Once the node is found, it is tested using a combination of frozen section and imprint cytology. The pathologist then says whether the node is involved or not with metastatic spread. If the node is deemed to be involved, the patient has a traditional axillary dissection. If the node is not involved, the patient is spared this. The sur- gical treatment of the primary continues while awaiting the results.
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Fig. 1. Intratumoral injection of methylene blue at the time of the procedure.
Fig. 2. Intraoperative location of node.
Fig. 3. Sentinel node partially stained with blue.
Intraoperative gamma camera locating sentinel node.
Problems with the technique
There may be ‘skip’ metastases that bypass the sentinel node and move to the next node in the chain. This is a recognised problem and addressed by doing the preopera- tive scan. All the nodes that show up should be removed (in the illustrated example there are 3 nodes). The background scan should be less than 10 x the count of the nodes that have been removed before the axilla is considered ade- quately biopsied. Occasionally, the node will take up dye but has lost the signal. This will occur if the procedure is done > 24 hours after the injection of the nanocolloid.
The node may not take up either the dye or the tracer. This occurs in < 90% of all cases and may be for technical rea- sons or because the node is replaced completely by tumour.
For whatever reason, the patient should have a standard axillary dissection.
Parasternal nodes are a ‘new’ problem that has been creat- ed by the technique. In the natural course of breast cancer, it is hardly ever necessary to manage the parasternal chain of nodes alone. Initially, if the sentinel node was found to be in the internal mammary chain, it was thought that no further action should be taken and that the patient should have a standard axillary dissection. However, breast cancer has been restaged to include the involvement of parasternal nodes. Since the new classification most surgeons would now look for the node because finding it to be involved would affect the subsequent oncological management of the patient.
There can be errors in sampling the correct node. The tech- nique should be used by a team who have validated their results and shown them to be representative of the axilla.
The form the audit should take is a subject debated by many international groups but all players acknowledge that, like any surgical technique, there is a steep learning curve.
The procedure costs about R4 000 if a preoperative scan is performed. The additional costs are balanced by a shorter hospital stay, increased mobility of the arm and no drain in the axilla.
Summary
Sentinel node biopsy in the management of breast cancer is a recent technique that has produced promising results. It is in keeping with the general trend in breast cancer manage- ment of making the surgery more patient- and tumour- specific.
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POINTS TO PONDERThere are currently about 40 wars in 35 countries and the impact of war on health is well known, according to a recent article in TheLancet. The 2002 WHO World report on violence and health states that 35 people die every hour as a direct result of armed conflict. War is the major cause of disability-adjusted life years lost in the global burden of disease. At least half the mortality and morbidity in current wars is in civilian populations and in many war-affected populations at least half of these civilians are younger than 18 years. But the direct violence of war only accounts for a relatively small proportion of this suffering. It is the destruction of health-sustaining infrastructure that accounts for far more. This includes the enormous
numbers of refugees that result from modern warfare. Just something to think about.
Lancet2004; 364: 384.
SINGLE SUTURE
Fig. 4. Cytological imprint of lymph node.
